I have been working on this thing, a small tank with temperature stratification, free surface (free slip boundary in CFX), inlet (opening static pressure), and some contractive outlets (mass flow rate).

water density (varying with temperature), temperature (varying with depth), pressure conditions were set through expressions in cfx-pre. And this simulation is steady.

However, it cannot be converged. See attached pics. I have attempted these time steps: 1 s, 20 s, 50 s, 120 s, 200 s (over flow).

what can I do to get this solved?
Do you guys have any suggestions? Thank u so much for your help.